Grease composition

ABSTRACT

A grease composition comprising base oil, one or more urea thickeners, (A) in the range of from 0.1 to 5 weight % of tungsten disulphide and (B) in the range of from 0.1 to 5 weight % of one or more of zinc dithiophosphates and/or one or more molybdenum dialkyl dithiocarbamates, based on the total weight of the grease composition.

This application claims priority from Japanese Patent Application No.2006-019709, filed on Jan. 27, 2006, which is incorporated herein byreference.

The present invention relates to a grease composition, in particular toa low friction grease composition whereby wear generated in lubricatedparts such as bearings or gears is suppressed.

Greases having excellent frictional wear characteristics are requiredin, for example, bearings or gears of mechanical devices in theautomobile, iron and steel, railway and other industries.

In particular, this is important for lubrication applications such asconstant velocity joints of automobiles, in which both rolling frictionand sliding friction are present and ball screws of driving gears in aninjection moulding machine or an electric pressing machine.

Conventionally, greases having excellent lubricating properties wereprepared by adding molybdenum disulphide to a lithium soap-thickenedgrease composition. Later in the art, greases have been prepared bysimultaneously adding an organic molybdenum compound and zincdithiophosphate to a urea-thickened grease. Such urea-thickened greaseshave been used with a view to reducing frictional wear characteristics.For example, laid-open Japanese Patent Application No. 62-207397describes a grease composition which comprises a sulphur-phosphorus typeextreme-pressure additive in which (a) molybdenum dialkyldithiocarbamate sulphide and (b) at least one member selected from thegroup consisting of a sulfurized oil, a sulfurized olefin, tricresylphosphate, trialkyl dithiophosphate, and a zinc dialkyl dithiophosphateare combined with each other as essential components.

Further, laid-open Japanese Patent Application No. 63-046299 discloses agrease composition in which additives, namely, molybdenum dialkyldithiocarbamate sulphide and molybdenum dithiophosphate and, optionally,zinc dithiophosphate are simultaneously blended in a urea-thickenedgrease.

However, in some jurisdictions such as Japan, commonmolybdenum-containing grease additives such as those described above aredefined as restricted substances. These chemical substances arerestricted in view of the danger of harmful effects on human health orecological systems (e.g. Japanese PRTR Law: Pollutant Release TransferRegister; Law for promotion of Chemical Management) and submission of anMSDS (Material Safety Data Sheet) on a product which contains aspecified amount or more of any of these substances may be required bythe laws of such jurisdictions.

Lead compounds and antimony compounds, which are also defined as PRTRrestricted substances, were used in grease compositions for many years.However, such compounds have been almost entirely replaced by sulphurtype extreme-pressure additives or the like which are free of theseproblems.

However, the afore-mentioned molybdenum compounds, in particular,molybdenum dialkyl dithiocarbamate sulphide, have an excellent effect inreducing friction and wear and it is hard to find a replacement formolybdenum dialkyl dithiocarbamate. Furthermore, even if such areplacement is added to the grease, a considerable amount thereof may berequired in order to secure a sufficiently low coefficient of friction.

Tungsten disulphide, is known as a solid lubricant and is a substancewhich is not defined as a PRTR restricted substance. Laid-open JapanesePatent Application No. 2003-301188 discloses that by adding tungstendisulphide to a lithium soap grease which contains polyoxypropylene andglyceryl ether as a base oil, a powder for density adjustment isprepared such that, when the grease that is used is liberated in water,this grease floats or sinks.

It is highly desirable to develop a grease composition imposing littleenvironmental load which has excellent friction and wear characteristicsand better safety by avoiding the use of molybdenum compounds that arethe subject of the afore-mentioned PRTR restrictions and/or being ableto reduce the amount thereof that is used in such a grease composition.

A grease composition has now been surprisingly developed which has lowfriction properties and excellent wear resistance by blending tungstendisulphide and zinc dithiophosphate and/or molybdenum dithiocarbamatewith a urea-thickened grease.

Accordingly, the present invention provides a grease composition,comprising base oil, one or more urea-thickeners, (A) in the range offrom 0.1 to 5 weight % of tungsten disulphide and (B) in the range offrom 0.1 to 5 weight % of one or more zinc dithiophosphates and/or oneor more molybdenum dithiocarbamates, based on the total weight of thegrease composition.

In a preferred embodiment of the present invention, the greasecomposition may further comprise (C) one or more molybdenumdithiophosphates.

According to the present invention, molybdenum compounds designated asPRTR restricted substances are not used, or the amount thereof which isused can be relatively reduced, and a grease composition havingexcellent performance in terms of friction and wear characteristics andhigh stability can thereby be obtained.

The base oil in the grease composition according to the presentinvention may be conveniently selected from mineral oils, vegetable oilsand synthetic oils such as ester oil, ether oil or hydrocarbon oil, ormixtures thereof.

The one or more urea thickeners in the grease composition of the presentinvention may be selected from urea compounds such as monourea, diurea,triurea, tetraurea or other polyureas.

Diurea compounds are easily obtained by the reaction of diisocyanate andmonourea; tetraurea compounds can be obtained by reaction ofdiisocyanate, monourea and diamines.

Examples of diisocyanates that may be used to make said urea compoundsinclude: diphenylmethane diisocyanate, tolylene diisocyanate, bitolylenediisocyanate and naphthylene diisocyanate.

Also, examples of monoamines that may be used to make said ureacompounds include octylamine, dodecylamine, stearylamine, oleylamine,aniline, paratoluidine and cyclohexylamine. Also, examples of diaminesthat may be used to make said urea compounds include ethylene diamine,propane diamine, butane diamine and phenylene diamine.

In a preferred embodiment, the grease composition of the presentinvention may comprise a total amount in the range of from 1 to 25weight % of said one or more urea thickeners, based on the total weightof said grease composition.

The grease composition of the present invention may further comprise oneor more additional thickeners such as metallic soaps, organic substancesor inorganic substances, for example, lithium soaps, lithium complexsoaps, sodium terephthalate, urea/urethane compounds and clays.

The tungsten disulphide which is employed as the afore-mentionedcomponent (A) in the grease composition of the present is preferably apowder having an average particle size of less than 10 μm obtained bythe Fisher method (Fisher Sub-sieve Sizer). More preferably, thetungsten disulphide which is employed is a powder having an averageparticle size of about 0.6 μm obtained by the afore-mentioned method.

The one or more zinc dithiophosphates which may be employed as theafore-mentioned component (B) in the grease composition of the presentinvention may be conveniently selected from zinc dialkyldithiophosphates and/or zinc diaryl dithiophosphates. Preferably, saidone or more zinc dithiophosphates may be selected from compounds offormula (I),

wherein R′ indicates primary or secondary alkyl groups or aryl groups,which may be the same or different. Preferably, primary or secondaryalkyl groups are employed as R′.

Specific examples of the above R′ include a methyl group, ethyl group,propyl group, isopropyl group, butyl group, secondary butyl group,isobutyl group, pentyl group, 4-methyl pentyl group, hexyl group,2-ethyl hexyl group, heptyl group, octyl group, nonyl group, decylgroup, isodecyl group, dodecyl group, tetradecyl group, hexadecyl group,octadecyl group, eicosyl group, docosyl group, tetracosyl group,cyclopentyl group, cyclohexyl group, methyl cyclohexyl group, ethylcyclohexyl group, dimethyl cyclohexyl group, cycloheptyl group, phenylgroup, tolyl group, xylyl group, ethyl phenyl group, propyl phenylgroup, butyl phenyl group, pentyl phenyl group, hexyl phenyl group,heptyl phenyl group, octyl phenyl group, nonyl phenyl group, decylphenyl group, dodecyl phenyl group, tetradecyl phenyl group, hexadecylphenyl group, octadecyl phenyl group, benzyl group and phenethyl group.

Specific examples of the above primary alkyl zinc dithiophosphateinclude zinc diisopropyl dithiophosphate and zinc diisobutyldithiophosphate and zinc diisodecyl dithiophosphate.

Also, specific examples of the above secondary dialkyl zincdithiophosphate include zinc mono or di-sec-butyl dithiophosphate, zincmono or di-sec-pentyl dithiophosphate and zinc mono ordi-4-methyl-2-pentyl dithiophosphate.

Specific examples of the above zinc aryl dithiophosphate include zincdi-para-dodecyl phenol dithiophosphate, zinc di-heptyl phenoldithiophosphate and zinc di-para-nonyl phenol dithiophosphate.

Preferred examples of the one or more molybdenum dialkyldithiocarbamates, which may be employed as component (B) in the greasecomposition of the present invention may be selected from compounds offormula (II),(R¹R²N—CS—S)₂Mo₂O_(m)S_(n)   (II)

wherein R¹ and R² respectively, may be independently selected from alkylgroups having a carbon number in the range of from 1 to 24 , preferablyin the range of from 3 to 18, m is an integer in the range of from 0 to3, n is an integer in the range of from 1 to 4 and m+n=4.

Specific examples of the afore-mentioned one or more molybdenum dialkyldithiocarbamates include molybdenum diethyl dithiocarbamate sulphide,molybdenum dipropyl dithiocarbamate sulphide, molybdenum dibutyldithiocarbamate sulphide, molybdenum dipentyl dithiocarbamate sulphide,molybdenum dihexyl dithiocarbamate sulphide, molybdenum dioctyldithiocarbamate sulphide, molybdenum didecyl dithiocarbamate sulphide,molybdenum didodecyl dithiocarbamate sulphide, molybdenumdi(butylphenyl) dithiocarbamate sulphide, molybdenum di(nonylphenyl)dithiocarbamate disulphide, oxy-molybdenum diethyl dithiocarbamatesulphide, oxy-molybdenum dipropyl dithiocarbamate sulphide,oxy-molybdenum dibutyl dithiocarbamate sulphide, oxy-molybdenum dipentyldithiocarbamate sulphide, oxy-molybdenum dihexyl dithiocarbamatesulphide, oxy-molybdenum dioctyl dithiocarbamate sulphide,oxy-molybdenum didecyl dithiocarbamate sulphide, oxy-molybdenumdidodecyl dithiocarbamate sulphide, oxy-molybdenum (butylphenyl)dithiocarbamate sulphide, oxy-molybdenum di(nonylphenyl) dithiocarbamatesulphide, and mixtures thereof.

Specific examples of the afore-mentioned one or more molybdenumdithiophosphates that may be employed as optional component (C) in thegrease composition of the present invention include molybdenum diethyldithiophosphate sulphide, molybdenum dipropyl dithiophosphate sulphide,molybdenum dibutyl dithiophosphate sulphide, molybdenum dipentyldithiophosphate sulphide, molybdenum dihexyl dithiophosphate sulphide,molybdenum dioctyl dithiophosphate sulphide, molybdenum didecyldithiophosphate sulphide, molybdenum didodecyl dithiophosphate sulphide,molybdenum di(butylphenyl) dithiophosphate sulphide, molybdenumdi(nonylphenyl) dithiophosphate disulphide, oxy-molybdenum diethyldithiophosphate sulphide, oxy-molybdenum dipropyl dithiophosphatesulphide, oxy-molybdenum dibutyl dithiophosphate sulphide,oxy-molybdenum dipentyl dithiophosphate sulphide, oxy-molybdenum dihexyldithiophosphate sulphide, oxy-molybdenum dioctyl dithiophosphatesulphide, oxy-molybdenum didecyl dithiophosphate sulphide,oxy-molybdenum didodecyl dithiophosphate sulphide, oxy-molybdenum(butylphenyl) dithiophosphate sulphide and oxy-molybdenumdi(nonylphenyl) dithiophosphate sulphide.

The afore-mentioned components (A) tungsten disulphide; and (B) one ormore zinc dithiophosphates and/or one or more molybdenumdithiocarbamates are respectively blended in the grease composition ofthe present invention in an amount in the range of from 0.1 to 5 weight%. Preferably, the afore-mentioned components (A) and (B) are eachblended in the grease composition of the present invention in an amountin the range of from 0.2 to 3 weight %, based on the total weight of thegrease composition. If the afore-mentioned components (A) and (B) areeach blended in an amount of less than 0.1 weight %, based on the totalweight of the grease composition, a low coefficient of friction cannotbe obtained and frictional wear is insufficiently improved. Furthermore,if the afore-mentioned components (A) and (B) are blended in an amountexceeding 5 weight %, based on the total weight of the greasecomposition, then no further increase in beneficial effect is seen.

The one or more molybdenum dithiophosphates (C) may be present in thegrease composition of the present invention in an amount in the range offrom 0.1 to 5 weight %, more preferably in the range of from 0.2 to 3weight %.

The grease composition of the present invention may further comprisevarious types of known additives such as antioxidants, for example,aminic and/or phenolic antioxidants, extreme pressure additives, forexample, olefin sulphides and/or oil sulphides, viscosity increasingagents, for example, polybutenes and/or polymethacrylates, solidlubricants, for example, molybdenum disulphide and/or boron nitride,metallic salts, for example, sulfonates, salicylates and/or phenatescapable of being used as antirust agents or structure stabilisers andphosphates and/or phosphates capable of being used as extremepressure/wear reducing agents.

The present invention further provides a method of reducing frictionand/or wear in the bearings, gears and/or joints of mechanical devices,wherein said method comprises lubricating said bearings, gears and/orjoints with a grease composition as hereinbefore described.

In addition, the present invention also provides a bearing, gear andjoint, characterised in that the grease composition as hereinbeforedescribed is used therein as the lubricant.

Furthermore, the present invention also provides the use of a greasecomposition as hereinbefore described to lubricate a bearing, a gearand/or a joint.

The present invention is described below with reference to the followingExamples, which are not intended to limit the scope of the invention inany way.

EXAMPLES

The grease compositions of Examples 1 to 7 and Comparative Examples 1 to8 were obtained by processing in a three-roll mill the base greases andadditives shown below with the blending compositions shown in Table 1 toTable 4.

[1] Base Grease

[1-1] Diurea Grease

-   -   Diphenyl methane-4,4′-diisocyanate (295.2 g) and octylamine        (304.8 g) were reacted in refined mineral oil (5400 g) having a        kinematic viscosity of about 15 mm²/s at 100° C., and the diurea        compound produced was uniformly dispersed to obtain a base        grease. The content of urea compound in the base grease was 10        weight %. The consistency of this diurea grease (25° C., 60 W)        according to JS-K2220 was 283 and its dropping point was 263° C.

[1-2] Tetraurea Grease

-   -   Diphenyl methane-4,4′ -diisocyanate (382.7 g), stearylamine        (411.4 g) and ethylene diamine (46.0 g) were reacted in refined        mineral oil (5160 g) having a kinematic viscosity of about 15        mm²/s at 100° C., and the urea compound produced was uniformly        dispersed to obtain a base grease. The content of the urea        compound in the base grease was 14 weight %. The consistency of        this tetraurea grease (25° C., 60 W) according to JS-K2220 was        285 and its dropping point was 202° C.        [2] Additives    -   [2-1] Tungsten disulphide (indicated in the Tables as WS₂) : a        tungsten disulphide powder having an average particle size of        0.6 μm, available under the trade designation of “Tanmik B” from        Nippon Lubricants Ltd. was employed.    -   [2-2] Zinc dithiophosphate (indicated in the Tables as Zn-DTP):        additive available under the trade designation “Lubrizol 1395”        from Lubrizol Inc. was employed.    -   [2-3] Molybdenum dithiocarbamate (indicated in the Tables as        Mo-DTC): additive available under the trade designation “Molyvan        A” from Vanderbilt Inc. was employed.    -   [2-4] Molybdenum dithiophosphate (indicated in the Tables as        Mo-DTP): additive available under the trade designation        “Sakuralube 300” from Asahi Electrochemical Industries Ltd. was        employed.    -   [2-5] Molybdenum disulphide (indicated in the Tables as MoS₂) :        Molybdenum disulphide having an average particle size of 0.7 μm        as manufactured by CLIMAX MOLYBDENUM UK Ltd was employed.    -   [2-6] Graphite (indicated in the Tables as graphite): graphite        as manufactured under the trade name “FAHN” by Fuji Graphite Ltd        was employed.        Falex Wear Resistance Test

Evaluation was conducted by carrying out the Falex Wear Resistance Testfor checking performance of the grease compositions obtained accordingto the Examples and Comparative Examples, and measuring the wearcoefficient and wear resistance (surface roughness of the test sample)in respect of these grease compositions.

The Falex wear resistance test is based on IP 241 (IP: Institute ofPetroleum, UK); tests are carried out in accordance with the followingconditions, to obtain a wear coefficient after completion of the test.Also, the Rmax (μm) (maximum surface roughness) of a reference testsample was measured.

Test Conditions

Rotational speed: 290±10 rpm

Temperature: room temperature (about 25° C.)

Load: 890N (200 lbf)

Time: 15 min

Amount of grease applied: about 1 gram applied to the test sample

Test Results

The results of the Falex wear resistance test are listed in Table 1 toTable 4. TABLE 1 Example 1 2 3 4 Compo- Base Diurea 96.0 98.0 96.0 95.0sition grease grease (weight Tetraurea — — — — %) grease Additives WS₂3.0 1.0 2.0 2.0 Zn-DTP 1.0 — — 1.0 Mo-DTC — 1.0 1.0 1.0 Mo-DTP — — 1.01.0 Total 100.0 100.0 100.0 100.0 Falex test Coefficient 0.081 0.0820.056 0.057 of fric- tion, μ Surface 9.3 10.1 6.6 5.9 roughness, Rmax(μm)

TABLE 2 Example 5 6 7 Compo- Base Diurea — — — sition grease grease(weight Tetraurea 96.0 96.0 96.0 %) grease Additives WS₂ 2.0 2.0 3.0Zn-DTP 1.0 1.0 — Mo-DTC 1.0 — 1.0 Mo-DTP — 1.0 — Total 100.0 100.0 100.0Falex test Coefficient 0.060 0.070 0.083 of fric- tion, μ Surface 7.85.9 8.1 roughness, Rmax (μm)

TABLE 3 Comparative Example 1 2 3 4 Compo- Base Diurea 97.0 97.0 97.097.0 sition grease grease (weight Tetraurea — — — — %) grease AdditivesWS₂ 3.0 — — — Zn-DTP — 3.0 — — Mo-DTC — — 3.0 — Mo-DTP — — — 3.0 Mo-S₂ —— — — Graphite — — — — Total 100.0 100.0 100.0 100.0 Falex testCoefficient 0.116 0.090 0.079 0.072 of fric- tion, μ Surface 36.2 21.935.0 17.2 roughness, Rmax (μm)

TABLE 4 Comparative Example 5 6 7 8 Compo- Base Diurea 98.0 — 96.0 -sition grease grease (weight Tetraurea — 98.0 — 96.0 %) grease AdditivesWS₂ — — — — Zn-DTP 1.0 1.0 — 1.0 Mo-DTC 1.0 1.0 1.0 — Mo-DTP — — 1.0 —Mo-S₂ — — 2.0 — Graphite — — — 3.0 Total 100.0 100.0 100.0 100.0 Falextest Coefficient 0.094 0.103 0.090 0.123 of fric- tion, μ Surface 12.111.3 14.0 31.2 roughness, Rmax (μm)

As is clear from Table 1 and Table 2, Examples 1 to 7 show excellentwear resistance, displaying low friction properties, with a frictionalcoefficient of approx. 0.056 to 0.083 in the Falex test, the maximumsurface roughness of the test sample being approx. 5.9 to 10.1 μm.

In contrast, as is clear from Table 3 and Table 4, the products ofComparative Examples 1 to 8 show in each case results that areunsatisfactory as regards both the coefficient of friction and wearresistance properties.

Specifically, the products of Comparative Examples 1, 2, 5, 7 and 8 havea high coefficient of friction and show large values of the maximumsurface roughness of the test sample. The products of ComparativeExamples 3 and 4 show comparatively low values of the coefficient offriction, but display large values of the maximum surface roughness ofthe test sample; it is inferred that in these cases the low coefficientof friction is displayed due to lowering of the contact area pressuredue to increased wear. In the case of the product of Comparative Example6, the maximum surface roughness of the test sample is comparativelyclose to that of the practical examples, but this product shows a highvalue of the coefficient of friction.

Also, as can be seen by comparing the Examples and Comparative Examples7, 8, in the case of molybdenum disulphide or graphite, which aresubstances of the same layer lattice structure as the tungstendisulphide used in the present invention, results satisfying both therequirement to provide an excellent low coefficient of friction and goodwear resistance as in the case of the practical examples are notobtained even when these are used together with for example Mo-DTC,Mo-DTP or Zn-DTP.

Thus, with the grease composition according to the present invention, anexcellent lubricating effect can be obtained without using molybdenumcompounds such as molybdenum dialkyl dithiocarbamate sulphide, or areduction in the amount of use of such molybdenum compounds can beachieved.

1. A grease composition comprising base oil, one or more ureathickeners, (A) in the range of from 0.1 to 5 weight % of tungstendisulphide and (B) in the range of from 0.1 to 5 weight % of one or morezinc dithiophosphates and/or one or more molybdenum dialkyldithiocarbamates, based on the total weight of the grease composition.2. Grease composition according to claim 1, wherein said greasecomposition further comprises (C) one or more molybdenumdithiophosphates.
 3. Grease composition according to claim 2, whereinthe one or more molybdenum dithiophosphates (C) are present in an amountin the range of from 0.1 to 5 weight %, based on the total weight of thegrease composition.
 4. Grease composition according to claim 1, whereinsaid one or more urea thickeners are present in a total amount in therange of from 1 to 25 weight %, based on the total weight of the greasecomposition.
 5. Grease composition according to claim 1, wherein thetungsten disulphide (A) is a powder having an average particle size ofless than 10 μm obtained by the Fisher method.
 6. Grease compositionaccording to claim 1, wherein the one or more zinc dithiophosphates areselected from compounds of formula (I),

wherein R′ indicates primary or secondary alkyl groups or aryl groups,which may be the same or different.
 7. Grease composition according toclaim 1, wherein the one or more zinc dithiophosphates are selected fromzinc diisopropyl dithiophosphate, zinc diisobutyl dithiophosphate, zincdiisodecyl dithiophosphate, zinc mono or di-sec-butyl dithiophosphate,zinc mono or di-sec-pentyl dithiophosphate, zinc mono ordi-4-methyl-2-pentyl dithiophosphate, zinc di-para-dodecyl phenoldithiophosphate, zinc di-heptyl phenol dithiophosphate and zincdi-para-nonylphenol dithiophosphate.
 8. Grease composition according toclaim 1, wherein the one or more molybdenum dithiocarbamates areselected from compounds of formula (II),(R¹R²N—CS—S)₂Mo₂O_(m)S_(n)   (II) wherein R¹ and R², respectively, maybe independently selected from alkyl groups having a carbon number inthe range of from 1 to 24, m is an integer in the range of from 0 to 3,n is an integer in the range of from 1 to 4 and m+n=4.
 9. A method ofreducing friction and/or wear in the bearings, gears and/or joints ofmechanical devices, wherein said method comprises lubricating saidbearings, gears and/or joints with a grease composition according toclaim
 1. 10. Use of a grease composition according to claim 1 tolubricate a bearing, a gear and/or a joint.
 11. Grease compositionaccording to claim 2, wherein said one or more urea thickeners arepresent in a total amount in the range of from 1 to 25 weight %, basedon the total weight of the grease composition.
 12. Grease compositionaccording to claim 3, wherein said one or more urea thickeners arepresent in a total amount in the range of from 1 to 25 weight %, basedon the total weight of the grease composition.
 13. Grease compositionaccording to claim 2, wherein the tungsten disulphide (A) is a powderhaving an average particle size of less than 10 μm obtained by theFisher method.
 14. Grease composition according to claim 3, wherein thetungsten disulphide (A) is a powder having an average particle size ofless than 10 μm obtained by the Fisher method.
 15. Grease compositionaccording to claim 4, wherein the tungsten disulphide (A) is a powderhaving an average particle size of less than 10 μm obtained by theFisher method.
 16. Grease composition according to claim 2, wherein theone or more zinc dithiophosphates are selected from compounds of formula(I),

wherein R′ indicates primary or secondary alkyl groups or aryl groups,which may be the same or different.
 17. Grease composition according toclaim 3, wherein the one or more zinc dithiophosphates are selected fromcompounds of formula (I),

wherein R′ indicates primary or secondary alkyl groups or aryl groups,which may be the same or different.
 18. Grease composition according toclaim 4, wherein the one or more zinc dithiophosphates are selected fromcompounds of formula (I),

wherein R′ indicates primary or secondary alkyl groups or aryl groups,which may be the same or different.
 19. Grease composition according toclaim 5, wherein the one or more zinc dithiophosphates are selected fromcompounds of formula (I),

wherein R′ indicates primary or secondary alkyl groups or aryl groups,which may be the same or different.
 20. Grease composition according toclaim 2, wherein the one or more zinc dithiophosphates are selected fromzinc diisopropyl dithiophosphate, zinc diisobutyl dithiophosphate, zincdiisodecyl dithiophosphate, zinc mono or di-sec-butyl dithiophosphate,zinc mono or di-sec-pentyl dithiophosphate, zinc mono ordi-4-methyl-2-pentyl dithiophosphate, zinc di-para-dodecyl phenoldithiophosphate, zinc di-heptyl phenol dithiophosphate and zincdi-para-nonylphenol dithiophosphate.